This invention relates to shoring systems for trenches. The shoring system comprises large shoring panels and strutting assemblies. Each shoring panel has laterally, on either end, a guide edge. The strutting assembly consists of a pair of vertical struts held oppositely apart by at least one horizontal strut. Each vertical strut of strutting assembly has lengthwise, laterally on either side, a U-shaped guide channel to receive cooperatively the guide edge provided on either end of each shoring panel.
The panels are arranged in pairs alongside the trench and held vertically parallel against either wall of the trench by a pair of strutting assemblies. Each strutting assembly slides on the opposite ends of the pair of panels. Several pairs of panels are successively connected by strutting assemblies creating a long shoring wall on either side of the trench.
Normally, the components of the shoring system are assembled together during first stage of excavation, up to 4 ft. deep. To begin with, one strutting assembly is installed in the trench having each vertical strut pressing respectively against either wall of the trench while the horizontal strut is maintained perpendicular to longitudinal axis of trench. A shoring panel slides within guide channel of each vertical strut pressing against respective wall of the trench. On the free end of each shoring panel slides the respective vertical strut of a second strutting assembly creating thereby a two sided shoring box called a shoring module. Afterward, each component of the shoring module is pushed down evenly as excavation progresses. Successive shoring modules are interconnected to shore the required length of the open trench. Normally, at one end of the trench (excavation section), a new shoring module is in installation process while at the other end (backfill section), a shoring module is in process to be removed from the ground. Hence, the shoring modules are moved along the trench from the backfill section to the excavation section in a leapfrog scheme.
There are several shoring devices used for securing the walls of open excavations and the working space inside it. A such shoring device, commonly called trench shield, has usually two panels held by individual spreaders pinned or bolted onto the extremities of each panel via flanges or fixed connectors. Principally, these devices are rigid in a sense that they do not allow relative movement between spreaders and panels and most of the time their installation is achieved after excavation.
Other types of shoring device, commonly called slide rail shoring systems, have a plurality of pairs of opposite rails spaced along the trench so that each pair of rails is supported by a strutting frame sliding in between them. Each rail support is provided on either side with guide channels where edges of large shoring panels slide interlocked within so that every two adjacent rails are connected with at least one shoring panel. Slide rails shoring system is currently used in the construction projects despite aversion in costs, weight and structural damages during utilization.
Knowing shoring device that has panels sliding vertically within excavation without using vertical support columns is disclosed in U.S. Pat. No. 6,224,296 (Fukumori). This device uses two pairs of large shoring panels. The first pair of panels, which shores the upper part of trench pressing against the excavation walls, is fixed at ground level. The second pair of panels slides within first pair shoring thereby the lower part of excavation. Both pairs of panels are connected and use sets of rigging to control the installation and removal of this device. Such device performs poorly in deep excavation and requires accurate installation regarding the space between first pair of panels their parallelism, etc. The removal of the panel is also associated with damages of guiding pair of panels.
U.S. Pat. Nos. 3,910,053 and 4,657,442 (Krings), U.S. Pat. Nos. 5,310,289 and 5,503,504 (Hess et al.), U.S. Pat. No. 6,164,874 (May) disclose various slide rail shoring system, all of them including multiple pairs of columns, spreader systems and large shoring panels. The support columns and the spreader systems used with these shoring systems are very heavy and are often hammered to push it down which often results with strong damages and heavy costs in maintenance.